This morning EPA administrator Scott Pruitt got the facts dead wrong on climate change. Here are his remarks and a quick recap of three fundamental facts that scientists at NASA, NOAA, NSF, EPA, and beyond have established over decades.
During an interview on CNBC, Pruitt’s answer to the question “Do you believe that it’s been proven that CO2 is the primary control knob for climate?” was:
“I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact, so no, I would not agree that it’s a primary contributor to the global warming that we see. But we don’t know that yet, we need to continue the debate we need to continue the review and analysis.”
Fact #1: Rising levels of carbon dioxide (CO2) are the primary contributor to global warming
This fact is not new. Scientists have investigated both natural and human contributions and have concluded that carbon dioxide (CO2) is the primary cause of global warming. The “apples to apples” comparison below uses the unit of radiative forcing (the effect caused by greenhouse gases in the atmosphere)—positive numbers indicate a contribution to warming and negative numbers a contribution to cooling. Carbon dioxide is the largest contributor to warming since both 1750 (see IPCC figure 8-15) and 1980 (see IPCC figure 8-20 below).
This figure compares the various factors that influence climate, both anthropogenic (human-driven) and natural. It shows “radiative forcing” (in watts per square meter). The higher a positive radiative forcing of a particular agent, the greater its role in global warming. (Source: IPCC fifth assessment report working group 1 figure 8-20.)
Fact #2: We have enough precision to measure human activity on carbon dioxide overload in the atmosphere
We can measure it! The scientists at the Environmental Protection Agency (EPA) have plotted the measurements of atmospheric carbon dioxide through 800,000 years of Earth’s history.
The earlier measurements are from ancient air locked in bubbles from ice cores, which come from research supported by the National Science Foundation (NSF) and other national and international sources. The modern measurements were begun by Charles David Keeling and continued by scientists at NOAA and others around the world. Atmospheric carbon dioxide measurement precision is accurate enough to know that today’s levels are not natural (see figure below).
Data source: EPA compilation of 10 underlying datasets. See www.epa.gov/climate-indicators for specific information. “Natural cycles” and “Precision is good enough…” labels added by B. Ekwurzel
We also have the ‘smoking gun’ evidence that this overload of carbon dioxide in our atmosphere is primarily from burning fossil fuels (see image below). Check out chapter 6 of the IPCC fifth assessment report for all the juicy details from the scientific community.
Carbon detectives: Not only can scientists measure the excess carbon dioxide (CO2) in the atmosphere, they can also detect the difference sources of the carbon atoms involved. Compared to other carbon sources, carbon from fossil fuels has a distinctly different “signature” (technically a measurement of carbon (i.e. δ13C pronounced “delta 13-C”) . The more negative the δ13C, the higher the proportion of carbon from fossil fuels. See IPCC fifth assessment report WG1 Chapter 6 for more details.
Fact #3: We have enough precision to measure the degree of impact from human activity
Consult the latest climate assessments or peer-reviewed papers on human fingerprints on climate change impacts for more information—there is plenty of it and we will delve further into it in future blog posts.
Finally, it is worth pointing out that administrator Pruitt’s blatant denial of well-established scientific facts is more than just egregious. It is also at odds with his testimony in his confirmation hearing and in no way changes his legal obligation to regulate carbon dioxide as a pollutant.